The invention relates generally to semiconductor devices and integrated circuit fabrication and, in particular, to device structures and fabrication methods for implementing a high performance heat shield.
Integrated circuit fabrication includes front-end-of-line (FEOL) processing, middle-of-line (MOL) processing, and back-end-of-line (BEOL) processing that are coordinated to produce chips. After active devices are formed by FEOL processing, MOL and BEOL processing are used to form an interconnect structure that includes metal lines and conductor-filled vias defining a three-dimensional framework of conductive paths. The conductive paths interconnect devices of the chip to power such devices and enable such devices to share and exchange information.
Metal lines in the interconnect structure have a small feature size and are subjected to high direct current densities during operation. These metal lines are highly susceptible to the occurrence of current-driven electromigration, which causes migration of metal atoms in the direction of electron flow due to momentum transfer between conducting electrons and diffusing metal atoms. Electromigration may operate to redistribute the metal. The metal redistribution may prompt failures from voids formed in the metal lines and failures from extrusions of metal from the metal lines into the surrounding dielectric material. As a result of these slightly different failure modes, voids may result in an open circuit and extrusions can cause a short circuit between adjacent metal lines.
Improved device structures and fabrication methods are needed for implementing a high performance heat shield.